Rapid development of wireless communication system requires high frequency and high power surface acoustic wave (SAW) filter. For SAW RF MEMS devices on diamond film, they have higher working frequency and more power endurance. A SAW RF MEMS filters on diamond film is designed. Its center frequency is 400MHz, and the line width of its Inter Digital Transducer (IDT) is 5μm. The diamond film on silicon substrate is customized by the CAEP ultra-hard material Co. 2μm thick ZnO piezoelectric film is deposited on diamond film by RF sputtering method. XRD analysis shows that the ZnO film has good C-axis orientation. IDT is fabricated by lift-off process. With delicate process control, designed delicate IDT pattern is acquired. The SAW RF MEMS filter prototype is finally packaged and tested. Its measured center frequency is about 378MHz, with insertion loss of 15.99dB.